The present invention relates to an alternator for motor vehicles, such as is discussed in DE 31 41 153 A1. It has a laminated stator core, originally developed in flat laminated form, having a three-phase stator winding, in which a magnetic field is induced rotating with the rotor by the rotor poles developed as claw-poles. Such generators have windings that have slot numbers that amount to an integral multiple of the pole number and the number of phases, in particular three-phase generators being commonly used that have 12 poles and 3 phases, as well as a slot number of 36. Furthermore, three-phase generators are also known in a 16-pole version as generators for motor vehicles having 48 slots. The number of holes q of this machine, which is given by the slot number N divided by the number of poles 2p and the number of phases m, is a whole number and has the value 1 in the above-mentioned case.
Generators having two or three hole windings are also known. A three-phase two-hole winding having 12 poles has 72 slots, and a three-phase three-hole winding has 108 slots. A three-phase generator in a 16-pole version then has 48 slots for a number of holes of q=1, and 96 slots for a number of holes of q=2.
Besides three-phase generators, 6-phase machines are also known for motor vehicles that have a number of holes of q=1 which, in the case of a 12-pole version then have 72 slots, and in the case of a 16-pole version of the machine, having a number of holes of q=1, 96 slots come about.
It is easy to see, from the previously named examples of motor vehicle generators currently in the market, that the selection of the possible slot numbers is small and that the slot number very rapidly assumes high values, whereby very narrow teeth that are difficult to stamp and small slot cross sections come about for the stator, which makes winding the stator more difficult, and gives rise to a poor fullness factor.
Furthermore, fractional slot windings are discussed in principle from the textbook, “Elektrische Maschinen (Electrical Machines)” by Bödefeld and Sequenz, Springer-Verlag Wien, 1962, pp 126 ff. However, these are used in practice only for large machines, as is also shown in the exemplary embodiments of the textbook, on p. 128. They have a number of holes q as the quotient of the slot number N, divided by the pole number 2p and the number of phases m, which is not a whole number but a fraction. In the construction of large-scale machines, fractional-slot windings are known particularly for large synchronous generators, in which windings are used that have a number of holes q=2.5 or 3.5.